1. Technical Field
The present invention relates to a teaching apparatus and a teaching method.
2. Related Art
When performing a process such as cleaning or heat treatment of semiconductor wafers, conventionally a wafer boat having slots that support a plurality of sheets of semiconductor wafers is employed. The semiconductor wafers are respectively inserted in each slot of the wafer boat for processing the plurality of semiconductor wafer sheets at a time. Upon completion of the process, the semiconductor wafer sheets are removed from the wafer boat.
For thus placing and removing the semiconductor wafers on and off the wafer boat, a carrying apparatus is employed.
To insert a semiconductor wafer held by a retainer of a carrying apparatus into a slot of a boat, conventionally an operator visually adjusts the positional relationship between the outer edge of the semiconductor wafer and the slot of the wafer boat. By such method, however, it is difficult to precisely insert the semiconductor wafer into the slot of the wafer boat. Actually the outer edge of the semiconductor wafer often collides with the wafer boat thus getting chipped or cracked.
Likewise, when removing the semiconductor wafer from the wafer boat, it is difficult to accurately adjust the position of the retainer of the carrying apparatus with that of the semiconductor wafer placed on the wafer boat, and the semiconductor wafer often suffers chipping and cracking.
Accordingly, methods of teaching the carrying apparatus a target position with respect to the wafer boat have been developed. A few examples of which are cited hereunder.
JP-A No. H09-8098 proposes, for a supporting boat (wafer boat) having a plurality of slots in a vertical heat-treatment apparatus, establishing a three-dimensional coordinate of an uppermost slot, a lowermost slot and at least one of the remaining slots, and storing such coordinate in the carrying apparatus. The carrying apparatus calculates a three-dimensional coordinate of said other slots based on the stored three-dimensional coordinate. And based on the calculated three-dimensional coordinate, the retainer of the carrying apparatus is driven, so as to insert semiconductor wafers into each slot one by one.
Also, JP-A No. 2004-241730 proposes an automatic teaching apparatus 108 as shown in FIGS. 15 and 16, including a dummy substrate 100 on which an x-direction slit 101 and a y-direction slit 102 are provided in predetermined positions, a sensor board 106 including an x-direction detection sensor 103 and a y-direction detection sensor 104 that respectively output a position signal corresponding to the slits 101, 102, and a z-direction detection sensor 105 that outputs a z-direction position signal, and a sensor signal processor 107.
In this automatic teaching apparatus 108, after the sensor board 106 is placed at a reference position in the wafer boat 109 (cassette module chamber), a robot arm (retainer) holding a dummy substrate 100 is located on the sensor board 106. Then the position of the dummy substrate 100 is determined such that the relationship between a position of the X-direction detection sensor A1(X1, Y1), a position of the Y-direction detection sensor A2 (X2, Y2), which are from the reference position O1 of the sensor board 106 coinciding with the central axis C, and a position of the X-direction detecting slit A1′(X1′, Y1′), a position of the Y-direction detecting slit A2′(X2′, Y2′), which is from the reference position O1′ of the dummy substrate 100 coinciding with the central axis C, satisfies A1=A1′ and A2=A2′, respectively.
The position that satisfies A1=A1′ and A2=A2′ is then stored in the carrying apparatus having the robot arm.
[Patented document 1] JP-A No. H09-8098
[Patented document 2] JP-A No. 2004-241730
The techniques according to the cited documents, however, still have a room for improvement in the following aspects.
Regarding the technique according to the patented document 1, when obtaining the three-dimensional coordinate of the uppermost slot, the lowermost slot and at least one of the remaining slots, actually the retainer is manually driven to be located close to the slot and positioned, and the three-dimensional coordinate of the retainer close to the slot is stored.
Here, the patented document 1 does not provide a specific method of positioning the retainer with respect to the slot.
On the other hand, with the technique according to the patented document 2, the width of the x-direction slit 101 and the y-direction slit 102 delimits the detection accuracy of a position of the X-direction detecting slit A1′ and a position of the Y-direction detecting slit position A2′.
In other words, the positioning accuracy of the dummy substrate 100 with respect to the sensor board 106 depends on the width of the x-direction slit 101 and the y-direction slit 102. Hence the widths of the x-direction slit 101 and the y-direction slit 102 have to be formed with high accuracy. This requires a complicated fabricating process for the dummy substrate 100 of the automatic teaching apparatus 108.